It is well-known that when an imagewise exposed silver halide color photographic light-sensitive material is processed in a color developer, the coupling reaction therein of a coupler with the oxidation product of an aromatic primary amine color developing agent produces a dye such as indophenol, indoaniline, indamine, azomethin, phenoxazine or phenazine to thereby form a dye image.
In such the photographic process, a subtractive color reproduction method is usually employed, in which there is used a silver halide color photographic material having blue-sensitive, green-sensitive and red-sensitive silver halide emulsion layers containing couplers having complementary color relations therewith. i.e., yellow, magenta and cyan color-forming couplers, respectively.
As the above yellow color image forming coupler there are acylacetanilide-type couplers: as the magenta color image forming coupler there are known pyrazolone, pyrazolobenzimidazole, pyrazolotriazole and indazolone-type couplers: and as the cyan color image forming coupler, there are generally used phenol and naphthol-type couplers.
The dye image thus obtained is requested not to fade or discolor even when exposed to light and stored under a high temperature/moisture condition over a long period of time. The non-dye-image-formed area of a silver halide photographic light-sensitive material (hereinafter called a color light-sensitive material) is requested to produce no yellow stain (hereinafter called Y-stain) attributable to light or heat/moisture.
In the case of the magenta coupler, however, it often comes into question that it produces much more Y-stain due to light or heat/moisure on the non-dye-image-formed area and discoloration due to light on the dye image area than do yellow and cyan couplers.
Couplers widely used for forming magenta dyes are 5-pyrazolone compounds. The dye formed from such the 5-pyrazolone compound has a subabsorption near 430 nm in addition to its principal absorption near 550 nm, which is a serious problem. In order to solve this problem, various studies have been made to date. Magenta couplers of the type of 5-pyrazolones having an anilino group in the third position thereof are useful particularly for making color image prints because the above-mentioned subabsorption thereof is small. These techniques are described in U.S. Pat. No. 2,343,703 and British Patent No. 1,059,994.
The above magenta coupler, however, has the disadvantage that a dye image formed therefrom has not only a poor image preservability. i.e., fastness against light, but also a significant Y-stain in its non-dye-image-formed area.
As other means to reduce the subabsorption near 430 nm of the above magenta couplers there have been proporsed the use of those magenta couplers such as the pyrazolobenzimidazoles described in British Patent No. 1,047,612; the indazolones described in U.S. Pat. No. 3,770,447; the 1H-pyrazolo[5,1-c]-1,2,4-triazole couplers described in U.S. Pat. No. 3,725,067, British Patent Nos. 1,252,418 and 1,334,515; the 1H-pyrazolo[1,5-b]-1,2,4-triazole couplers described in Research Disclosure 24531 (1984): the 1H-pyrazolo[1,5-c]-1,2,3-triazole couplers described in Research Disclosure 24626 (1984): the lH-imidazoI,2-b]pyrazole couplers described in Japanese Patent O.P.I. Publication No. 162548/1984 and Research Disclosure 24531: the 1H-pyrazolo[1,5-]pyrazole couplers described in Research Disclosure 24230 (1984); and the 1H-pyrazolo[1,5-d]tetrazole couplers described in Research Disclosure 24220 (1984). Of these magenta couplers, the dyes formed from the 1H-pyrazolo[5,1-c]-1,2,4-triazole couplers, 1H-pyrazolo[1,5-b]pyrazole couplers and 1H-pyrazolo[1,5-d]tetrazole couplers are suitable for color reproduction since their absorption near 430 nm is significantly smaller than that of the dyes formed from 5-pyrazolones having an anilino group in the third position thereof, and advantageous because they produce very little Y-stain caused by light and heat/moisture in the non-dye-image-formed area.
However, the fastness to light of the azomethine dyes formed from these couplers is significantly low, and the dyes are liable to be discolored by light, so that they, when used, will impair the characteristics of light-sensitive materials. particularly color light-sensitive materials for making color prints.
Japanese Patent O.P.I. Publication No. 125732/1984 proposes a technique for improving the light fastness of a magenta dye image obtained from the 1H-pyrazolo[5,1-c]-1,2,4-triazole magenta coupler by using a phenol-type compound or a phenylether-type compound in combination therewith.
Even the above technique, however, is insufficient to prevent the above magenta dye image from light fading. and it is almost impossible for the technique to prevent the dye image from discoloration.